SUMMARY
This volume is part of the latest Erlbaum series, New directions in communication disorders research: Integrative approaches; it is a collection of sixteen essays on language acquisition and language disorders in children written in honour of Robin Chapman. Chapter 1 is written by Robin Chapman herself, and it is reprinted from a previously published article (Chapman, Reference Chapman2000). It sets the scene for what is to follow and provides a summary of the themes and issues that are discussed in more detail throughout the volume. The chapter has four main parts: (1) historical accounts of development and variability; (2) recent advances in methodologies; (3) genetic contributions to language development; and (4) the role of language input. A summary of the different theoretical approaches to child language acquisition is offered, and the interactionist perspective is established as the favoured one over other perspectives on how language is acquired. Evidence in support of this perspective is provided in the remaining three parts of the chapter. Thus a brief overview of recent methodological advances follows, with consideration given to cross-linguistic studies, including studies of specific language impairment (SLI), cultural variation in language acquisition, language disorders in children including genetic syndromes, contexts of language use, new task paradigms including preferential looking, online language processing and neuroimaging, computer archiving such as CHILDES, and connectionist modelling. The chapter discusses genetic contributions to language development in more detail, including issues of heterogeneity in SLI, with short reviews of family aggregation studies, pedigree studies, twin studies of typically developing children and those of children with language disorders, and adoption studies. The role of language input is given a prominent place in the chapter, with a detailed description of Hart and Risley's (Reference Hart and Risley1992, Reference Hart and Risley1995) studies. There is a very useful appendix at the end of the chapter, which provides several tables detailing stages of pragmatic, semantic and syntactic development, and a table providing variability in language learning in typically developing children.
Chapter 2 by Kent and Vorperian discusses a possible biological model of how the integration of anatomic, motor and sensory factors is necessary for speech development in children. This chapter does not directly consider speech disorders; however, the authors do mention in the end that this model should be able to account for atypical speech development once the various types of information have been integrated into a biological model that can account for typical speech development.
In Chapter 3 Ellis Weismer provides empirical data and a discussion of how one can distinguish between toddlers who may be initially delayed but catch up with their peers (late talkers) from those who will have persistent language difficulties and will later be diagnosed with SLI. This is a crucial issue, as early identification of children who are at risk for SLI will lead to early intervention for affected children. The results of the project show that language development in late talkers is in many ways similar to language development of typically developing children. For example, at 2 ; 0, late talkers have a similar number of verbs in their vocabulary to younger children matched on total vocabulary level, which is not the case for children with SLI, who seem to have fewer verbs in their vocabularies (Leonard, Reference Leonard1998). On the other hand, late talkers were found to be slower to start combining words compared to typical talkers matched on total vocabulary level, which suggests differences between language development in late and typical talkers. The author also identifies important issues for further research, such as the need to explain factors that underlie differential trajectories of those late talkers who fully catch up with their peers from those who proceed to have language difficulties, which are on the lower end of the ‘language endowment spectrum’. The term ‘language endowment’ come from Rescorla's (Reference Rescorla2000, Reference Rescorla2002) work in which a spectrum of language ability is proposed, with a continuum ranging from children with typical language development to late bloomers who start late but catch up to late talkers with more persistent delays to those with SLI.
Chapter 4 by Klee, Gavin and Stokes continues with the issue of SLI by considering possible clinical markers for the disorder. This chapter directly links to Robin Chapman, who, together with Jon Miller, developed the first computerized analysis of language samples (Systematic Analysis of Language Transcripts, SALT). The chapter starts with a comprehensive review of the literature on clinical markers, which has used two different statistical procedures: group mean differences and discriminant analysis. The literature review is followed by two studies: the first one examines the relationship between measures of utterance length (MLU) and lexical diversity (D) in two groups of young typically developing children: a group of British-English speakers and a group of American-English speakers. The data are compared to previous data collected from young children acquiring Cantonese and to data from an earlier sample of typically developing American children reported by Miller & Chapman (Reference Miller and Chapman1981). In the second study, the authors investigated whether the combination of MLU, D and age can be used as a clinical marker to differentiate young English-speaking children with and without SLI. Based on the results and their analyses of both studies, the authors concluded that a composite of age, MLU and D might serve as a clinical marker of English-speaking children with SLI who are three years of age, but not those who are two years of age. The authors acknowledge the need for further research, including larger sample sizes, and also call for studies to report likelihood ratios and associated confidence intervals.
Chapter 5 by Crais discusses the importance of gesture for language development from an interactionist perspective. The author applies the two generalizations about language learning introduced by Robin Chapman in Chapter 1 – (1) old forms are used to express new meanings; and (2) new forms are used to express old meanings – to gestures. A number of examples are cited from different studies in order to substantiate these generalizations and support the conclusion that gesture development predicts later language development. The chapter also evaluates the literature on disordered populations, arguing that gesture use can be a predictor for identifying children with communication deficits.
Chapters 6 to 9 deal with language development in populations with autistic spectrum and genetic disorders. Paul, Chawarska, Klin and Volkmar provide a useful overview of language development in Autistic Spectrum Disorders (ASD) from infancy to preschool years, emphasizing the fact that, although communication deficits are a core feature of ASD and slow language acquisition is common, there is individual variation and there may be several subgroups of children on the spectrum. The authors also provide an overview of those patterns of communication, such as pronoun reversal, echolalia, intonation and pragmatic impairment, which are specific to ASD. Longitudinal data from the Yale Developmental Disabilities Clinic are then presented. The study includes toddlers aged between 1 ; 4 and 3 ; 1 at initial assessment. All children were seen at two time points and there was a comprehensive range of assessments of language, cognitive, motor, social and adaptive areas, including standardized and non-standardized measures. The results showed that both for children who were verbal and for those who were not verbal in their second year, sound production appears ahead of social communication and understanding of language. This chapter is very strongly embedded within current theoretical explanations of language impairment and the authors discuss at length the issue of dissociations as it applies to ASD, but also as it applies to genetic syndromes (such as Williams syndrome Fragile X) as well as SLI. The authors adopt the neuro-constructivist view in order to address the question of how dissociations may arise and then proceed by detailing dissociations between expressive and receptive language (with expressive language ahead of receptive) and between lexical and phonological production (phonological production ahead of lexical) in early communicative development in ASD.
Aspects of language in children with autism and adolescents and young adults with Fragile X syndrome (FXS) are presented in Chapter 7, written by Abbeduto and McDuffie. The chapter reports results from a longitudinal study of twenty-nine children with autism with a mean age of 2 ; 8 at the initial visit. It was found that attention following by the children predicts their vocabulary development. The authors aim to show that the nativist approach to language acquisition cannot account for the language profiles of FXS and that these are best accounted for by the Child Talk model proposed by Chapman. The statement in the conclusion of the chapter that ‘the nativists assume that language learning is a modular process of mastering abstract, context free rules’ (p. 208) is somewhat oversimplified and can be misleading to the uninformed reader.
Fragile X syndrome is further discussed in Chapter 8 by Johnson-Glenberg. New data are presented that measure the memory and reading skills of both typically developing individuals and those with FXS. The chapter then focuses on a specific ongoing study that is investigating memory and reading abilities in a group of participants with FXS and a mental age matched control group. Unfortunately this paper does not take a developmental perspective for the disordered group, which is duly acknowledged and a number of research questions for future research are put forward.
Whilst the previous eight chapters discuss language development in monolingual contexts, Chapter 9 by Kay-Raining Bird is a literature review of language acquisition in bilingual contexts both for typically developing populations and populations with developmental disorders, including children with Down syndrome, those with SLI and children with intellectual disability. The author pays special attention to the issue of assessment and clinical intervention for bilingual children with communication disorders and ultimately argues that simultaneous bilingual acquisition is to be encouraged for children with Down syndrome.
Chapter 10 by Johnson discusses development of communicative competence of children who are vulnerable because of environmental and family circumstances, and in particular children who are prenatally exposed to drugs. A description of a case study of one such child is included to show how the child's immediate environment affected the development of his social communication skills. The chapter emphasizes how it is crucial to take an interactionist perspective when considering cases of vulnerable children, although development of language and communication skills is considered after the initial acquisition and therefore it is unclear how an interactionist approach best predicts outcomes in this case.
Chapter 11 by Dollaghan follows one of the guiding themes of Robin Chapman's work, which is to study language disorders within the context of typical developmental processes. Dollaghan reports findings from a project which investigated the use of verbs by children with language delay due to otitis media when compared to typically developing children. The author proposes new ways of thinking about lexical and verb diversity and the relationship between lexical items and utterance production by proposing the concepts of small-world networks and hubs. The idea is that rather than looking at a verb in terms of its semantics (e.g. ‘light vs. heavy’) and syntax (e.g. its argument structure), verbs could be looked at in terms of their connections not just to lexical items that have similar characteristics but also to lexical items that seem quite disparate.
Chapter 12 by Miller provides an excellent historical overview of the development of one of the most useful computer assisted programs for analyzing spontaneous speech, the Systematic Analysis of Language Transcripts (SALT). Chapter 13 by Boudreau bring us back to language in children with language impairments, and in this chapter the focus is on narrative abilities. The chapter includes an excellent review of the literature on narrative abilities in both typically developing children (preschool through the school ages) and those with language impairments, and discusses the issue of whether narratives are due to performance or competence limitations. The author then presents data on narrative abilities that come from a current pilot project of eight children with language impairment and argues that a limited capacity model can best explain difficulties that children with language impairment have with narrative production.
Chapter 14 by Calculator argues that developmental issues must be taken into consideration when decisions are made by clinicians to provide Augmentative and Alternative Communication systems to prelinguistic children with severe impairments. Unlike the previous chapters, which deal primarily with language production, Chapter 15 by Milosky and Skarakis-Doyle focuses on language comprehension in young children at the level of the discourse and provides sample tasks from their own research emphasizing the importance of assessing language comprehension in children and also thinking about remediation. The final chapter is written by Robin Chapman and it provides a summary of her own path and the influences that have shaped her point of view with regard to language learning and disorders, which she embeds in a discussion of the issues that have been raised and discussed by the contributors to this volume.
EVALUATION
This collection of essays is a welcome contribution to the field of language acquisition and disorders of language and communication. The majority of the chapters provide new empirical data on different facets of language development in typically developing children and in a range of atypical populations in a number of different contexts, including standardized tests, experimental procedures and naturalistic spontaneous speech data elicited through conversations and narratives. Given that the essays are written in honour of Robin Chapman, most of the contributors aimed to embed their research and findings within the context of Robin Chapman's work, ideas and theoretical views on language learning. Some chapters meet this aim remarkably well, whereas others do it less successfully. For example, when discussing language in vulnerable children, there is an obvious attempt to explain findings from an interactionist perspective of language acquisition. The evidence offered, however, is rather weak and somewhat contradictory. If a child who was prenatally exposed to drugs, which placed him at heightened risk for developmental difficulties and who had a mother who was not very responsive to the child, still managed to acquire language successfully and had age-appropriate communication skills at age 3 ; 0, it is difficult to see how one could be persuaded that environmental influences are crucial in influencing the child's acquisition of language. Nevertheless, the collection of papers presented in the book gives a wide snapshot of some of the current ideas about language acquisition and disorders today, it considers a number of clinical implications which have followed from research findings and it sets the scene for further investigations and discussion in the field.
